Snaffles are obtained through smoking marijuana. They are not, contrary to popular belief, the same as the munchies. A requirement of the munchies is that one is genuinely hungry. The snaffles are when you reach the stage where you feel physically bloated, and would (under sober circumstances) never continue eating, yet you do.

Oh man, I had the snaffles so bad last night, I thought I was going to explode.